The present invention relates to an optical switch. More specifically, the present invention relates to an optical switch suitable for an optical communication system, an optical storage device, an optical arithmetic unit, an optical recorder, an optical printer and so forth, particularly, for the optical communication system in which a multichannel optical switch is desired to perform switching for each specific beam.
With recent developments in optical communication technology, optical switches have been sought that allow high-speed response, size reduction, high integration, low power consumption, and reduction of signal attenuation.
Conventionally-known optical switches include the ones in which liquid crystal is used, optical fibers are moved by a mechanical device using an electromagnet, a micromirror is used and so forth.
However, the optical switch using liquid crystal performs switching on the basis of molecular orientation, so that the optical switch has been slow in response and has not been easily adapted to optical communication requiring high-speed communication. There also has been a problem in that utilization efficiency of light is low since a polarizing plate has to be employed.
In the optical switch in which optical fibers are moved by a mechanical device using an electromagnet, the device could not be reduced in size and it has been difficult to meet the demands for a high degree of integration. Additionally, there has been a problem in that power consumption is large as switching is performed by the mechanical operations of an electromagnet.
In the optical switch using a micromirror, the manufacturing process becomes complex and the manufacturing costs are thus high, which is troublesome. There also has been a problem in that attenuation of signals is large since the light is required to propagate through the atmosphere.
In addition to these optical switches, an optical switch is proposed that performs switching by utilizing the change in refractive indexes of optical waveguides due to electro-optic effects during the application of electric fields to the optical waveguides.
However, in this type of optical switch, there is a problem in that the switch is likely to be affected by interference from electric fields applied by other switches by which the other optical waveguides are controlled. Particularly, when an optical switch is reduced in size, electrodes to apply electric fields to each optical waveguide inevitably get close to each other, increasing the interfering effect of electric fields between adjacent optical waveguides and generating errors due to crosstalk and so forth, which has been troublesome.
Additionally, an optical switching element has been proposed that has: a light guide portion for performing light transmission by confining light internally by total reflection; an optical switching portion for extracting the light trapped internally to the outside of the light guide portion when the optical switching portion is in contact with the light guide portion, and then reflecting the extracted light into the direction of the desired light guide portion; and a driving portion for driving the optical switching portion (Japanese Unexamined Patent Application Publication No. 11-202222).
However, this optical switching element is configured to let the light guide portion extend light transmission of input light only in one direction. At the same time, the switching element unintentionally outputs the light that is input to the light guide portion, to the outside by contacting the switching portion to an unspecific total reflecting plane of the light guide portion. In other words, the switch only turns light on or off. Accordingly, the following configurations cannot be achieved: a switching element as an optical switch that outputs specific input light after switching the optical path thereof to a specific plurality of output side ends; an optical switch that outputs a specific plurality of input light to specific output ends by switching each optical path of the input light; and a multichannel optical switch that outputs a specific plurality of input light after switching the input light to a specific plurality of output ends. Although the switching element may be applicable to objects such as an image display, it has been practically difficult to apply the switching element to an optical communication system.
Moreover, in addition to the configuration whereby the light guide portion extends light transmission only in one direction, the optical switching element is configured to utilize infinitely repeated total reflection of the light guide portion. Thus, an emitting direction at the switching portion, in consideration of refraction at an interface between atmosphere and the light guide portion, is restricted to an actuator angle than the total reflection angle thereof; in other words, an almost vertical direction to the total reflecting plane. Even in this sense, switching to transmit light into different directions for each specific light could not be performed.
The present invention has been made in view of the aforementioned problems, and the object of the present invention is to provide an optical switch suitable for an optical communication system that solves the problems of conventional optical switches, and allows for low power consumption, a high-speed response, size reduction and high integration, significant reduction of signal attenuation and, furthermore, switching per specific input light.
The present inventors, after thorough research to solve the above-noted problems, have discovered that the object mentioned above may be achieved by providing a light transmission portion having optical transmission channels, consisting of optical wave guiding bodies, in at least three directions with a light reflecting plane at one part on a surface of a light transmission portion, facing an optical path-changing portion, as a starting point. The optical path-changing portion is contacted or separated from the light reflecting plane of the light transmission portion at wavelength levels of input light based on displacement of an actuator portion.
Specifically, according to the present invention, there is provided an optical switch including at least a light transmission portion, an optical path-changing portion, and an actuator portion. The light transmission portion has a light reflecting plane provided at least at one part of a plane facing the optical path-changing portion to totally reflect light. Light transmission channels are provided, which consist of optical wave guiding bodies, in at least three directions with the light reflecting plane functioning as a starting point. The optical path-changing portion is provided in proximity to the light reflecting plane of the light transmission portion in a movable condition and has a light introduction member made of a transparent material and a light reflection member for totally reflecting light. The actuator portion has a mechanism that is displaced by external signals and transmits the displacement to the optical path-changing portion. The optical path-changing portion is contacted or separated from the light reflecting plane of the light transmission portion by displacement of the actuator portion in response to external signals. An optical path where the light input to the light transmission channel is totally reflected at the light reflecting plane of the light transmission portion and is transmitted to a specific light transmission channel on an output side, is switched to another optical path where the light input to the light transmission channel is taken to the light introduction member, and is totally reflected at the light reflection member and is transmitted to a specific light transmission channel on an output side.
It is preferable, in the present invention, that the actuator portion has a piezoelectric/electrostrictive element including a piezoelectric/electrostrictive layer and at least one pair of electrodes arranged on one part of the piezoelectric/electrostrictive layer. A vibrating member is provided and is in contact with at least one part of the piezoelectric/electrostrictive element to support the piezoelectric/electrostrictive element and converts strain of the piezoelectric/electrostrictive layer into bending displacement or vibrations. A fixing member is provided to fix at least one part of the vibrating member so as to vibrate the vibrating member. A displacement transmission member is provided and is arranged between the optical path-changing portion and the piezoelectric/electrostrictive element and transmits displacement of the piezoelectric/electrostrictive element to the optical path-changing portion.
It is preferable that a substrate of ceramics is constituted by unitarily sintering the vibrating member and the fixing member, and that a recessed portion or a hollow portion is formed in the substrate which gives the vibrating member a thin structure. Moreover, the actuator may be a so-called stacked actuator composed of a laminated body in which an anode layer of linking multiple layers as anodes and a cathode layer of linking multiple layers as cathodes are alternately laminated on the piezoelectric/electrostrictive layer composed of ceramics therebetween.
In the present invention, it is more preferable that the light transmission portion includes two or more layers having different light refractive indexes, and that the light transmission channels of the light transmission portion include optical waveguides.
Additionally, the light transmission portion may be configured by joining at least two optical wave guiding bodies to one optical wave guiding body so as to form light transmission channels in at least three directions with the light reflecting plane of the light transmission portion acting as a starting point. Moreover, in the present invention, it is preferable that a condenser lens or a collimator lens is arranged at each of a plurality of light-signal input ends and/or light-signal output ends of the light transmission portion, and that light signals are input and output through the condenser lens or the collimator lens.
Moreover, in the present invention, the light reflection member may be a light reflecting film that is integrally formed on a plane of the light introduction member on the side of the displacement transmission member.
Additionally, according to the present invention, a multichannel optical switch having a plurality of the optical switches mentioned above is provided.
As an embodiment in a multichannel optical switch of the present invention, a multichannel optical switch may be included in which each light transmission channel of a plurality of optical switches is formed of a single light transmission portion. The multichannel optical switch is configured to let a part of each light transmission channel share a part of channels by crossing each other.
Other embodiments in multichannel optical switches of the present invention may include the following examples: A switch in which a plurality of optical switches are constituted by linking one input-side channel to one output-side channel between adjacent optical switches, and switching the light input from input ends in an optical switch at each optical path-changing portion of a plurality of optical switches including the optical switch. A switch in which a plurality of optical switches are constituted by at least one optical switch having a plurality of input-side channels and at least one optical switch having a plurality of output-side channels and in which one input-side channel is linked to one output-side channel between adjacent optical switches, and switching the light input from input ends of a plurality of optical switches at the optical path-changing portion of the plurality of optical switches. A switch having a plurality of optical switches in which one input-side channel is linked to one output-side channel between adjacent optical switches by means of optical fiber, and switching at least the light input from input ends in an optical switch at each optical path-changing portion of a plurality of optical switches, or the like.
In the present invention, the multichannel switch, furthermore, may include: the switch in which a plurality of the multichannel switches are arranged in a row; or the switch that has a plurality of the multichannel optical switches, and in which each multichannel optical switch is arranged by locating at least one part of output ends themselves of each light transmission channel in each multichannel optical switch in an arc condition with an input end in an outer light transmission channel, which is disposed separately from each multichannel optical switch, at a center.
Furthermore, the multichannel optical switch may include: the switch in which an optical divider or an optical coupler is joined to a light-signal input end or a light-signal output end of each light transmission channel in the multichannel optical switches to branch or collect at least one part of light transmission channels; the switch in which an optical demultiplexer or an optical multiplexer is joined to a light-signal input end or a light-signal output end of each light transmission channel in the multichannel optical switches to branch or collect at least one part of light transmission channels; and the switch in which each output end or each input end of a plurality of the multichannel optical switches is linked to a plurality of input ends or output ends in at least another similar multichannel optical switch.
Moreover, in the multichannel optical switch of the present invention, it is preferable that each optical path-changing portion has a light reflection member and at least two kinds of light reflection angles are shared among the optical path-changing portions.
The whole description of the specification of U.S. patent application Ser. No. 09/799,329 filed on Dec. 27, 2000 is cited here for reference.